title: Alternative photosynthetic electron transport pathways during anaerobiosis in the green alga Chlamydomonas reinhardtii.
abstract: Oxygenic photosynthesis uses light as energy source to generate an oxidant powerful enough to oxidize water into oxygen, electrons and protons. Upon linear electron transport, electrons extracted from water are used to reduce NADP(+) to NADPH. The oxygen molecule has been integrated into the cellular metabolism, both as the most efficient electron acceptor during respiratory electron transport and as oxidant and/or "substrate" in a number of biosynthetic pathways. Though photosynthesis of higher plants, algae and cyanobacteria produces oxygen, there are conditions under which this type of photosynthesis operates under hypoxic or anaerobic conditions. In the unicellular green alga Chlamydomonas reinhardtii, this condition is induced by sulfur deficiency, and it results in the production of molecular hydrogen. Research on this biotechnologically relevant phenomenon has contributed largely to new insights into additional pathways of photosynthetic electron transport, which extend the former concept of linear electron flow by far. This review summarizes the recent knowledge about various electron sources and sinks of oxygenic photosynthesis besides water and NADP(+) in the context of their contribution to hydrogen photoproduction by C. reinhardtii. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
authors.affiliation: Ruhr Universität Bochum, Fakultät für Biologie und Biotechnologie, Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie, 44780 Bochum, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Hemschemeier
authors.forename: Thomas
authors.initials: T
authors.lastname: Happe
mesh_terms: D000693:Anaerobiosis / Q000502:physiology*; D016825:Chlamydomonas reinhardtii / Q000502:physiology*; D004579:Electron Transport / Q000502:physiology*; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D010940:Plant Proteins / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D045222:Electron Transport Chain Complex Proteins; D010940:Plant Proteins; D014867:Water; D009249:NADP; D010100:Oxygen